Color compositions

ABSTRACT

The present invention includes a paint or coating composition comprising an organic pigment or dye complexed to the surface of a layered or fibrous inorganic clay. A wide variety of paint colors can be obtained by varying the pH during the preparation as well as by varying the synthesis conditions and changing particle size of the clay. The paint has unprecedented stability.

[0001] This application claims benefit of priority to U.S. ProvisionalApplication Serial No. 60/390,049, filed Jun. 19, 2002, the entirecontents of which are incorporated by reference.

[0002] The government may own rights in the present invention pursuantto GSA Strategic Metals Grant No. 26-3000-57.

BACKGROUND OF THE INVENTION

[0003] I. Field of the Invention

[0004] The present invention relates to the field of paints and morespecifically provides a novel long lasting, stable powder that can beincorporated into paints, plastics, and cements.

[0005] II. Description of Related Art

[0006] In the scientific literature, the term Maya blue refers to a“turquoise” brilliant shade of blue that is found on murals andarchaeological artifacts, for example, throughout Mesoamerica. It isdescribed in the literature as being composed of palygorskite clay andindigo, that when mixed and heated, produce the stable brilliant bluecolor similar to that found in Mesoamerica. Any proposed methods ofpreparation were done for the intention of trying to replicate the bluecolor found at the historical sites and to reproduce the techniquesemployed by the original Maya.

[0007] H. Van Olphen, Rutherford Gettens, Edwin Littman, Anna Shepard,and Luis Torres, were perhaps some of the most prominently involvedscientists in the examination of organic/inorganic complex paint fromthe 1960's to the 1980's. In the early studies, only Littman and VanOlphen published information specifically on the synthesis oforganic/inorganic complex (13, 14, 9, 10). While their work neverdefinitively described the Maya technique for making the colorant, orexplained the stability of the organic/inorganic complex, the results oftheir two decades of studies with respect to the ancient paint laid afoundation of knowledge for future investigators.

[0008] Littman has synthesized indigo-attapulgite complexes and verifiedthat his synthetic version was indistinguishable from the originalpigments found in the pre-Hispanic murals and artifacts (9, 10). Theprepared samples had the same physical and chemical characteristics asthe authentic Maya blue examined. Littman concluded that the remarkablestability of the attapulgite was due to the heat treatment theattapulgite received during the synthesis. Others have also synthesizedcompounds similar to that of Maya blue by a number of routes (30). Theyemployed the Gettens test to determine whether the laboratory synthesisof Maya blue was indeed authentic with the same chemical resistantproperties (3). The test was necessary because initial attempts ofsimply mixing the palygorskite clay produced the color of Maya blue butthe mixture did not possess the same chemical properties as the originalorganic/inorganic complex samples.

[0009] The literature for Maya paint compositions does not provideinformation with respect to varying the color for the paint compositionbased on altering the pH and particle size; nor does there appear to bemention of using alternate dye or pigment systems as described in thepresent invention. Formulations of paints based on the paint compositionof the present invention with resins or polymeric systems have not beenrealized either according to the literature. The only known literaturediscussions of pH pertain to the alkaline pH required to reduce theindigo prior to contacting it with the clay (9, 10). Furthermore, thereis a lack of understanding regarding the chemistry for producing stableand nontoxic paint systems by combining dyes and pigments with fibrousand layered clays.

[0010] Therefore, it would be advantageous to provide a novel paintcomposition that is stable and nontoxic.

SUMMARY OF THE INVENTION

[0011] Thus, in accordance with the present invention, there is provideda coating composition comprising (a) a molecular derivative of indigo;and (b) a fibrous or layered clay, wherein the coating composition isused for coloring surfaces. The color/hue of the composition isdetermined by the concentration of the dye and pH of the composition.The particle size of the coating composition may be between about 0.01μm and 20 μm, or more particularly between about 0.1 μm and 2 μm. Thefibrous clay may be selected from a palygorskite clay, a sepiolite clay,or a mixture of a palygorskite and a sepiolite clay. The layered claymay be a kaolinite, bentonite, nontronite, or mordenite clay. Themolecular derivative of indigo may be dibromoindigo or thioindigo. Thecoating composition may be a powder or a liquid. The coating compositionmay be resistant to decomposition by light, acids, alkalis, and/orsolvents.

[0012] In another embodiment, there is provided a compositioncomprising:

[0013] wherein R₁-R₈ are individually H, CH₃, CH₂CH₃, F, Cl, Br, I, CN,OH, SH, OCH₃ or OCH₂CH₃; R₉-R₁₁ are individually SiO₃, SiOH or H₂O; Y isN, O, S, or Se; X is O or S; M^((n+)) is Al, Sc, Ti, V, Cr, Mn, Fe, Co,Ni, Cu, Pt, Pd or Zn; and n is 1, 2, 3, or 4.

[0014] In yet another embodiment, there is provided a formulationcomprising (a) a molecular derivative of indigo; (b) a palygorskiteclay, a sepiolite clay, or a mixture of a palygorskite and a sepioliteclay; (c) a polymer; and (d) an organic binding agent.

[0015] In still yet another embodiment, there is provided a formulationcomprising (a) a molecular derivative of indigo; (b) a palygorskiteclay, a sepiolite clay, or a mixture of a palygorskite and a sepioliteclay; and (c) a gum arabic; a linseed oil; a copal; a polycarbonate; anegg tempura; or a turpentine.

[0016] In a further embodiment, there is provided a shapeable moldingmaterial comprising (a) a molecular derivative of indigo; (b) apalygorskite clay, a sepiolite clay, or a mixture of a palygorskite anda sepiolite clay; and (c) a cement, a plastic or a polymer.

[0017] In still a further embodiment, there is provided a shapeable tilematerial comprising (a) a molecular derivative of indigo; (b) apalygorskite clay, a sepiolite clay, or a mixture of a palygorskite anda sepiolite clay; and (c) a cement, a plastic or a polymer.

[0018] In still yet a further embodiment, there is provided a method ofproducing a coating composition comprising (a) providing a molecularderivative of indigo; (b) combining the molecular derivative of indigowith a fibrous or layered clay to form a coating composition; (c)heating the coating composition; and (d) adjusting the pH of the dye orpigment composition. The method may further comprise: (a) treating thecoating composition with acid to remove impurities from the clay; (b)applying the coating composition to a surface; (c) blending the coatingcomposition with a polymer or organic binder; or homogenizing the dyecomposition by blending, grinding, milling or stirring.

[0019] The heating may comprise heating at a temperature of between 100°C. and 300° C., or more particularly between 115° C. and 150° C. Theheating may last up to four days. The coating composition may containwater, may have a pH between about 3 and about 7.5, may contain a dye inthe range of 0.01% to 20% by weight, may contain a molecular derivativeof indigo in the range of about 0.1% to 7% by weight, or moreparticularly by about 6% by weight at neutral or acidic pH. The fibrousclay may be a palygorskite clay, a sepiolite clay, or a mixture of apalygorskite and a sepiolite clay. The layered clay may be a kaolinite,bentonite, nontronite, or mordenite clay. The particle size of thecoating composition is between about 0.01 μm and 20 μm, or moreparticularly between about 0.1 μm and 2 μm. The molecular derivative ofindigo may be thioindigo or dibromoindigo. The method may furthercomprise adding a binding agent to the coating composition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following drawings form part of the present specification andare included to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

[0021]FIG. 1—Color variations of synthetic organic/inorganic complexesprepared using various concentrations of indigo derivatives. Verticallyshown are the effects of pH on a synthetic sample made with 4% wt.Indigo derivatives.

[0022]FIG. 2—Color changes as a function of temperature and heating timeof synthetic organic/inorganic complexes.

[0023]FIG. 3—Synchrotron X-ray Diffraction of Attagel (palygorskite) andorganic/inorganic complex at 25° C. and 140° C. Simulated diffraction ofIndigo derivatives are also shown.

[0024]FIG. 4—IR Analysis of crystal violet mixed with palygorskite clay.Temperatures are room temperature (25° C.) and after heating andreaction at 140° C. The cationic exchange reaction with the clay doesnot produce a color change, and thus it does not chemically alter the IRspectra.

[0025]FIG. 5—IR Analysis of maya blue (indigo pigment mixed withpalygorskite clay). One is at room temperature (25° C.), where there isno chemical reaction or color change when the indigo is merely mixedwith the clay. After 140° C. heating and reaction of the mixture, the IRspectra clearly changes. The changes in the peaks are indicative of anew chemical interaction between the indigo and clay.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention includes a color composition of mattercomprising organic pigments and dyes complexed to the surface ofinorganic clays. These organic/inorganic hybrid materials are useful aspaints and coatings for artisan and industrial purposes, as well ascolor compositions to be used with cements, plastics, papers andpolymers. Upon grinding and heating the organic and inorganic componentas solid mixtures or in aqueous solutions, the resulting colorcomposition has unprecedented stability relative to the originalstarting material alone. The inorganic component is either a layeredclay or a fibrous clay. The fibrous clay can be either palygorskite orsepiolite clay. The layered clay may be, for example, a kaolinite,bentonite, nontronite, or mordenite clay. The organic component is anorganic dye or pigment of which some examples are found in the bookColor Chemistry, 2^(nd) ed. (33). Using the clay with various dyes orpigments results in achieving a color composition possessing a widevariety of colors.

[0027] By changing the pH during the preparation of such colorcompositions control of the final composition color can be attainedwithin any given set of clay/pigment materials. Additionally, byselecting a particular particle size of the clay starting material, awide range of colors and hues can also be created. The color compositioncan be suspended in an organic binder, resins or polymers, depending onthe final application. The paint powder can also be formulated with agum arabic; a linseed oil; a copal; a polycarbonate; an egg tempura; ora turpentine, depending on the final application.

[0028] The coating composition may be applied to a surface by any of themeans known in the art for paint application such as by brushing orspraying. Also, multiple shapeable materials can be formed byincorporating the color composition of the present invention in liquid,powder, or solid form, or as an emulsion with cements, plastics orpolymers, to produce molding materials, tiles, concrete and other formsproduced using layered or fibrous clays. The color composition can alsobe incorporated into portland cement concrete materials to be used ascolor markers on road surfaces or bridges. Some examples of portlandcement concrete materials are covered in the U.S. Department ofTransportation Manual (31) and other concrete materials are covered inConcrete (12). Methods of incorporating the color compositions intocement or concrete can be found in Cement Science, In concreteAdmixtures Handbook: Properties, Science, and Technology (26).

[0029] I. Dyes

[0030] The color for the color composition comes from an organic dye orpigment. This chromophore may be a molecular derivative of indigo suchas dibromoindigo or thioindigo. Other derivatives of indigo may also beused to vary the color or other physical properties of the colorcomposition. These chromophores are shown in Scheme 1. The chromophoremay also be a different derivative, such as one containing an additionalconjugated ring or ligand.

[0031] wherein R₁-R₈ are individually H, CH₃, CH₂CH₃, F, Cl, Br, I, CN,OH, SH, OCH₃ or OCH₂CH₃; R₉-R₁₁ are individually SiO₃, SiOH or H₂O; Y isN, O, S, or Se; X is O or S; M^((n+)) is Al, Sc, Ti, V, Cr, Mn, Fe, Co,Ni, Cu, Pt, Pd or Zn; and n is 1, 2, 3, or 4.

[0032] II. Clays

[0033] As used herein, the term “clay” refers to layered clays as wellas fibrous clay. The fibrous clay is preferentially a palygorskite clay,a sepiolite clay, or a mixture of palygorskite and sepiolite clays. Themixture may be in any ratio. For example, it may be 50% palygorskite and50% sepiolite or it may be 10%/90%, 20%/80%, 30%/70%, 40%/60%, 60%/40%,70%/30%, 80%/20%, or 90%/10% (palygorskite/sepiolite). As used hereinthe term palygorskite and attapulgity are used interchangeably to referto the same type of clay. The layered clay may be, for example, akaolinite, bentonite, nontronite, or mordenite clay.

[0034] Previous work has shown that synthesis of comparableorganic/inorganic complex paint using clays with plate-like structures,including kaolinite, bentonite, nontronite, and mordenite all produce ablue colored pigment, but without the stability of the indigoderivative/palygorskite complex (13, 14). This indicates that thepossible stability of the Maya blue pigment is due to the fiber-likestructure of the clays used since the use of plate-like clays had notbeen shown to yield a stable pigment (13, 14, 9, 10).

[0035] The particle size of the clay may be varied. It is preferentiallybetween 0.01 μm and 20 μm, 0.05 μm and 10 μm or more preferably between0.1 μm and 2 μm. As the color changes with the size of the particles,varying the particle size allows for greater control of color. Smallerparticles will tend to be more blue in hue where the larger particlestend towards green in hue.

[0036] III. Polymers, Binding Agents and Modifiers

[0037] One or more binding agent or modifiers may be added to the paintcomposition to increase stability, uniformity, spreadability, adhesion,coating thickness etc. Binding agents and modifiers are well known inthe art of paint formulation and may be included in the current coatingcomposition. Binding agents such as solvent-containing binding agents(acryl, cyclized rubber, butyl rubber, hydrocarbon resin,α-methylstyrene-acrylonitrile copolymers, polyester imide, acryl acidbutyl esters, polyacrylic acid esters, polyurethanes, aliphaticpolyurethanes and chloro sulphonated polyethylene), and thermoplasticmaterials (polyolefins, α-ethylstyrene-acrylonitrile copolymers,polyester imide and polyamide) may be added to the paint composition.Similarly, polymers such as acrylate, styrene acrylate, acrylonitrilecopolymer, polyethylene, polyethylene oxidate, chlorosulfonatedpolyethylene, ethylene-acrylic acid copolymer, methacrylate,vinylpyrrolidone-vinyl acetate copolymer, vinylidene chloride copolymer,polyvinylpyrrolidone, polyisopropyl acrylate, polyurethane, cyclizedrubber, butyl rubber, hydrocarbon resin, α-methylstyrene-acrylonitrilecopolymer, polyester imide, acryl acid butyl esters, or polyacrylic acidesters may be added.

[0038] The paint composition can be blended with a variety of othermedium including gum arabic, linseed oil, copal, polycarbonate, eggtempura, and turpentine to create blended systems. The blended paintcolor can be altered depending on the medium in which it is blended.Grinding the initial powder to various particle sizes prior to or duringblending with a medium can result in color control.

[0039] IV. Color Optimization

[0040] A series of experiments were developed to optimize the propertiesand hues of the synthetic versions of organic/inorganic complex. Thesynthetic versions of organic/inorganic complex were tested forstability using the Gettens test; however, the inventors have found thatthe Gettens test is limited and alternative methods such as IR have alsobeen employed in these studies. Specifically, by examining the effectsof dye or pigment, such as dibromoindigo, concentration, pH, andparticle size, a paint possessing a color remarkably similar and stableto that of a known organic/inorganic complex was developed. Thestability of the complex can be seen by its resistance to decompositionwhen exposed to light. Since the complex is formed with both organic andinorganic components, the stability is much higher than if only organiccomponents were used. Based on these studies, a wide range of blues andgreen hues were developed as well. The present invention has establisheda synthetic route that can be reproduced based on the instrumentalanalysis that have established the chemical interactions necessary for astable reproducible paint. This invention has led to a fundamentalunderstanding of the complex chemical interaction between indigoderivatives and palygorskite or other types of clays.

[0041] If one wishes to reproduce a “color” that resembles anothercolor, there are many limitations on how the two could be compared. Theconcept of color is only accurate if one considers that color does notexist independently of normal color vision. Spectroscopic analyses suchas UV/Visible are unavailing considering that certain indigo derivativesare practically insoluble in aqueous acids and aqueous alkalinesolutions. Indigo derivatives are soluble in some non-polar solvents butonly in the concentration range of 10⁻⁵-10⁻⁶ mol/L. Heating a mixture ofan indigo derivative and palygorskite may indeed produce a color that‘looks’ like the organic/inorganic complex seen at so manyarchaeological sites. But in the absence of knowing the precisequantity, conditions, and binding agents that the Maya used, thereproductions described in the literature could only be analyzed by anaesthetic visual comparison and represent different chemical techniquesfor producing a Maya Blue “type” organic/inorganic paint powder. Thevarious shades of organic/inorganic complex that the inventors producedas a function of altering the concentration of indigo derivatives andthe pH of the solution are shown in FIG. 1.

[0042] Early attempts at recreating Maya blue were made by firstreducing indigo with sodium hydrosulfite, as shown in FIG. 1, thencontacting it with clay and exposing the mixture to air (14). It wasalso found that heating the paint pigments at moderate temperaturescaused the treated pigments to become stable to hot concentrated mineralacids, stable to acetone extraction, and stable to color change whenexposed to heat (250° C.) (13, 14).

[0043] Heat is introduced to the sample to dramatically increase thestability and can be used to alter the color. Both the temperature andthe duration of heating affect the stability and color of the finalpaint composition. Heating may be done in an oven, or by other means ofraising the temperature to the desired setting. The temperature shouldbe between 100° C. and 300° C. as the paint composition starts todecompose above this point. More preferentially, the heating temperatureshould be between 100° C. and 200° C. or between 115° C. and 150° C. Theduration the sample is heated can also be varied, depending upon therequirements for the particular application. The heat may be applied forup to several hours, 1 day, 2 days, 3 days or up to 4 days.

[0044] The paint composition produced in this manner is resistant todecomposition by light. This means that, when exposed to strong sunlightor other light sources as is common for painted surfaces, thecomposition will not noticeably change in color and the intensity, asmeasured by IR spectroscopy or x-ray diffraction, and will not decreasemore than 10% over a 1 year period. The composition is also resistant todecomposition by acids, alkalis, and solvents. When exposed to acidic orbasic solutions, the composition will not noticeably change in color andthe intensity, as measured by IR spectroscopy or x-ray diffraction, willnot decrease more than 10% over a 1 year period.

[0045] V. General Method for Producing Color Composition

[0046] The general method for producing a color composition comprises of(a) providing a molecular derivative of indigo or any cationic organicdye or cationic pigment. The derivative of indigo can be selected fromany indigo derivative shown in Scheme 1. The amount of dye or pigmentused can be in the range of 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%,0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%,0.9%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%,11.0%, 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, or 20.0%by weight or more preferably 0.1% to 7% by weight or ideally at about 6%by weight.

[0047] The next step (b) can consist of combining the molecularderivative of indigo with an appropriate weight of fibrous clay, such asa palygorskite clay, a sepiolite clay, or a mixture of a palygorskiteand a sepiolite clay, or a layered clay, such as a kaolinite, bentonite,nontronite, or mordenite clay to form a color composition. Step (b)further comprises the grinding of the dye or pigment with the layered orfibrous clay which can be carried out in, but not limited to, a blender,industrial blender, industrial mixer, shear blender, or a precise solidstate blender. The clay and the dye may be ground separately and thenground together or they may be combined and ground to both mix the twocomponents in order to obtain the preferred particle size. If the clayis already at the preferred size, the clay and indigo may be mixedtogether without grinding. Techniques for grinding and blending the dyeand clay compositions are found in Mixing of Solids (32), Powder andBulk Solids Handling Processes (6), or Bulk Solids Mixing (5).De-ionized water may be added during blending to attain a homogenizedmixture. The clay or clay mixture should be ground to obtain particlesof between about 0.005 μm and 50 μm, 0.01 μm and 20 μm, 0.05 μm and 10μm, or more particularly between about 0.1 μm and 2 μm. A range ofparticles sizes is expected, but over 60% or over 80% or over 90% orover 95% or over 99% of the particles should be the desired size. Forexample, when the particles are ground to about 2.0 μm, 80% of theparticles should be between 1.7 μm and 2.3 μm.

[0048] The next step comprises (c) heating the color composition. Theheating may comprise heating at a temperature of 100° C., 110° C., 115°C., 120° C., 125° C., 130° C., 135° C., 140° C., 145° C., 150° C., 155°C., 160° C., 165° C., 170° C., 175° C., 180° C., 185° C., 190° C., 195°C., 200° C., 205° C., 210° C., 215° C., 220° C., 225° C., 230° C., 235°C., 240° C., 245° C., 250° C., 255° C., 260° C., 265° C., 270° C., 275°C., 280° C., 285° C., 290° C., 295° C. or 300° C., or more particularlybetween 115° C. and 150° C. The heating may be for several hours, 1 day,2 days, 3 days, or may last up to four days. The heating can be carriedout in, but not limited to, a batch oven, a drying oven, an infraredoven, or a powder coating oven.

[0049] Next the pH of the color composition may be adjusted to an acidicor neutral pH, depending on the final color desired. Exemplary examplesof the acid used to adjust the pH comprise: any protonic acid, H₂SO₄,HClO₄, HClO₃, H₃PO₄, HNO3, HCN, HF, HBr, HI, H₃O⁺, or CH₃COOH, or morepreferably HCl. Exemplary examples of the base used to adjust the pHcomprise: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂ or morepreferably NaOH. The pH of the color composition can be 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, or 12. The pH of the system can be monitored with apH meter that is calibrated with buffers of pH 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, or 12.

[0050] Additional steps in making the color composition may comprise:treating the color composition with acid such as but not limited to anyprotonic acid, H₂SO₄, HClO₄, HClO₃, H₃PO₄, HNO₃, HCN, HF, HBr, HI, H₃O⁺,or CH₃COOH, or more preferably HCl, to remove impurities from the clay;applying the color composition to a surface; blending the colorcomposition with a polymer, plastic or organic binder as discussed inEncyclopedia of Polymer Science and Engineering, 2^(nd) ed. (11) andPaint and Surface Coatings: Theory and Practice, 2^(nd) ed. (8).

[0051] The following patents are included as examples to demonstratecertain embodiments of the invention. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention. U.S. Pat. No. 3,950,180 covers the method ofmanufacturing color compositions that include zeolite andmontmorillonite. U.S. Pat. No. 5,061,290 covers the method of usingindigo derivatives as a dyeing agent. U.S. Pat. No. 4,246,036 covers themethod of manufacturing color compositions that are comprised ofasbestos-cement. U.S. Pat. No. 4,640,862 covers color compositions thatare used for coating an expanded polystyrene “drop-out” ceiling tile.U.S. Pat. No. 4,868,018 covers color compositions that are used with amixture of epoxy resin, epoxy resin hardener, and portland cement toform a coating which can be applied to a surface to form simulatedmarble products. U.S. Pat. No. 4,874,433 covers a method forencapsulating color compositions in and/or to a zeolite. U.S. Pat. No.5,574,081 covers a method of manufacturing waterborne clay-containingemulsion paints with improved application performance using colorcompositions. U.S. Pat. No. 5,972,049 covers the method of manufacturingand using color compositions to form dye carriers used in the dyeingprocess for hydrophobic textiles. U.S. Pat. No. 5,993,920 covers themethod of manufacturing and using color compositions with stone powderand/or cement powder, fine sawdust and/or the heart of a kaoliang stalkand other materials to form an incombustible artificial marble. U.S.Pat. No. 6,339,084 covers the method of manufacturing thiazine-indigopigments. U.S. Pat. No. 6,402,826 covers the method and manufacturing ofcolor compositions for paper coating.

[0052] As used herein, the term “organic/inorganic complex” refers to acomplexation of one or more organic molecules with one or more inorganicmolecules. As used herein the term “color composition” refers to apigment or dye complexed to a fibrous or a layered clay. As used herein,the term “coating composition” is synonymous with “color composition”and “paint powder”. As used herein, the term “cement” refers to Portlandcement types I, II, III, IV, IA, IIA, IIIA or as covered in TheChemistry of Portland Cement, 2^(nd) ed. (2); or any cement typediscussed in the Dictionary of Cement Manufacture & Technology ZementWoerterbuch (1). The chemistry of cements use in the present inventionis covered in The Chemistry of Cements, 2 ^(nd) volume (29). As usedherein, the term clay refers to a fibrous clay, such as, but not limitedto, a palygorskite or a sepiolite clay or a layered clay, such as, butnot limited to, kaolinite, bentonite, nontronite, or mordenite clay.

[0053] As used herein, the term “about” means within 25% of the statedvalue, or more preferentially within 15% of the value. As used hereinthe specification, “a” or “an” may mean one or more. As used herein inthe claim(s), when used in conjunction with the word “comprising”, thewords “a” or “an” may mean one or more than one. As used herein“another” may mean at least a second or more.

VI. EXAMPLES

[0054] The following examples are included to demonstrate preferredembodiments of the invention. It should be appreciated by those of skillin the art that the techniques disclosed in the examples which followrepresent techniques discovered by the inventor to function well in thepractice of the invention, and thus can be considered to constitutepreferred modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention.

Prophetic Example 1 Indigo Derivatives Concentration Experiments

[0055] A 0.05 g sample of indigo derivatives (from BASF) was suspendedin ˜50 ml of water. Sodium hydrosulfite, 0.03 g, and 15 drops of 1 MNaOH were added to the solution to reduce the indigo derivative. Thesolution was heated to 90° C. while stirring with a magnetic stirrer.The solution remained blue, at which point an additional 0.1 g of sodiumhydrosulfite was added. The solution turned clear indicating that theindigo derivative had been reduced and was now soluble. The leucoindigoderivative was then poured over 5 g of palygorskite clay, and wasstirred. Immediately upon contact with the clay and being exposed toair, the solution turned dark blue. The solution was placed in the ovenat 125° C. for four days, at which point it resembled the color oforganic/inorganic complex. The hue was slightly lighter and less intensethan that of original organic/inorganic complex; hence, a series of claypigments were prepared with various concentrations to examine colordifferences as a function of the concentration of indigo derivative.Additionally, it was determined, as has been cited in the literature,that it was not necessary to reduce the indigo derivatives prior toblending it with the clay. Thus, the rest of the syntheticorganic/inorganic complex samples were prepared without reducing theindigo derivatives first.

[0056] Preparing a series of organic/inorganic complex samples withvarying concentrations was accomplished by grinding a 0.01 g, 0.02 g,0.03 g, 0.04 g, and 0.05 g of indigo derivatives with 5.00 g ofpalygorskite clay, respectively. Each concentration series was thenplaced in a blender with 100 ml of de-ionized water and blended forseveral minutes to ensure that a homogenous mixture was obtained. Thecorresponding solutions were placed in a 250 ml beaker in the oven at125° C. for four days. It was confirmed by I.R. that a blue color couldalso be produced simply by grinding the indigo derivative and claywithout water, provided the two were subsequently heated. For laterstudies, the simplest method of grinding was employed.

Example 2 pH Experiments of Synthetic Organic/Inorganic Complex

[0057] Synthetic samples were prepared using either sodium hydroxide orsodium hydrochloride to prepare the samples in acidic or basic solution.For the pH studies, 0.1 g of indigo was ground with 5.0 g of clay fourtimes to obtain four samples. To each ground mixture was added 100 ml DIwater, and dropwise either 1 M NaOH, or 1 M HCl to obtain solutions withpH's of 4, 7, 9, and 11. The pH of the system was monitored with a pHmeter that had been calibrated with buffers of pH 4, 7, and 11.

[0058] As shown in FIG. 1, the colors arranged horizontally, preparedwith increasing concentrations of indigo, visually range from a palebluish-green to a darker grayish blue-green. The variations of colorseen in the vertical direction range from grayish blue-green under basicconditions to brighter, vibrant blues at neutral to acidic pH. Visually,the organic/inorganic complex prepared with the highest percentage (2%)of indigo derivatives under neutral pH conditions was closest inresembling the ‘authentic’ organic/inorganic complex.

Example 3 Mixing of Organic/Inorganic Complex

[0059] Synthesis of organic/inorganic complex requires grinding ormilling. It is known that under mechanical milling the fiber bundles candisaggregate and the ends become splayed. At the frayed ends, the bondstrength of the tetrahedral layers is reduced such that the guest indigomolecule can enter the channel and pry apart the weaker layers to createa superlattice structure. Furthermore, as organic molecules interactwith the clay surface there is a reorientation of the OH— groups whichinitiates the elastic deformation of the interlayer spacing, thusallowing penetration of the guest molecule. The inventors have solidstate NMR and IR evidence of how the OH— groups on the palygorskitesurface reorient during this process. This reorientation, or change inSi—O—Si bond angle is directly related to the adsorption of indigoderivative to the external surface.

Example 4 Temperature Study of Indigo/Palygorskite

[0060] One interesting observation is that one can visually see thegradual color changes of the clay/indigo mixture while it is heated inthe oven. To monitor these color changes and consequently, monitor thechemical interaction, a synthetic organic/inorganic complex was made aspreviously described. During the process the reaction was stopped atvarious temperatures. Initially, 0.3 g of indigo derivative was blendedwith 4.7 g of palygorskite. One gram of this mixture was placed in avial. The remaining sample mixture was heated for 24 hours at 100° C. atwhich point another gram was taken from the mixture and placed in avial. The remaining mixture was heated an additional 24 hours at 140° C.and then placed in a vial for later analyses. The clay samples, at 25°C., 100° C., and 140° C. were analyzed using synchrotron x-raydiffraction, x-ray diffraction simulations and IR spectroscopy. Arepresentation of the colors and hues of the starting materials andchanges in the color and hue upon heating are shown in FIG. 3.

Example 5 Synchrotron X-Ray Diffraction of Synthetic Organic/InorganicComplex

[0061] The palygorskite clay (Attagel) and organic/inorganic complexprepared at 25° C. and 140° C. were run at SSRL on beam line 2-1. Thediffraction of indigo was simulated using Cerius 2. The resulting datawere compared and are shown in FIG. 3. The diffraction pattern of theunheated mixture of clay and indigo (25° C.) still has peaks due to thecrystalline phase of indigo. Once the clay and indigo are heatedtogether to make the 140° C. sample, the indigo phase no longer givesdiffraction peaks. Clearly, the crystal structure of indigo has beendisrupted as a consequence of its binding to the clay surface.

Example 6 Particle Size Experiment Example

[0062] Two indigo derivative samples (0.05 g each) were separatelyground in a blender with 4.7 g of palygorskite clay. One of the claysamples was 0.1 μm in size and the other was 2 μm in particle size. Eachmixture was heated to 125° C. for three days. The sample prepared withthe 2 μm particle size clay had a darker green hue. The sample preparedwith the 0.1 μm size clay had a darker blue hue.

Example 7 Other Dye/Pigment Systems

[0063] 0.05 g of thioindigo was ground with palygorskite and heated inthe oven for three days at 125° C. A remarkable color change (frommagenta red to royal blue) was observed during the heating process.Other dyes also may be used in this manner.

Example 8 Cationic Organic/Inorganic Complexes

[0064] Several cationic dyes were reacted with the palygorskite clay.Each dye (0.1 g each) was separately ground in a blender with 4.9 g ofpalygorskite clay and 100 mL of water. The mixtures were then placed inthe oven at 125oC until the water evaporated. The samples were ground ina mortar and pestle and then any excess dye that was not bound to theclay was extracted with water or an appropriate solvent. For thecationic complexes, no changes in color were observed because thebinding mechanism does not involve electron charge transfer, as is thecase with neutral molecules. Infrared analysis following excess dyeextraction was used to analyze the final clay/cationic dye complex(FIGS. 4 and 5). The list of successfully employed cationic dyesincludes crystal violet, aniline blue, methylene blue, victoria blue R,malachite green oxalate, methylene green, neutral red, quinoldine red,alpahazurine A, janus green B, ethyl violet. The compounds have thegeneral structure:

[0065] Clay Surface—O⁻H⁺+R⁺X⁻ reacts to give: Clay surface—O⁻R⁺+H⁺X⁻

[0066] All of the methods disclosed and claimed herein can be made andexecuted without undue experimentation in light of the presentdisclosure. While the compositions and methods of this invention havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to the methodsand in the steps or in the sequence of steps of the method describedherein without departing from the concept, spirit and scope of theinvention. More specifically, it will be apparent that certain agentswhich are both chemically and physiologically related may be substitutedfor the agents described herein while the same or similar results wouldbe achieved. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the spirit, scope andconcept of the invention as defined by the appended claims.

REFERENCES

[0067] The following references, to the extent that they provideexemplary procedural or other details supplementary to those set forthherein, are specifically incorporated herein by reference:

[0068] 1. Amerongen, C. V. Dictionary of Cement Manufacture & TechnologyZement Woerterbuch French & European Pubns., Oct. 1, 1986.

[0069] 2. Bogue, R. H. The Chemistry of Portland Cement, 2d ed. NewYork: Reinhold Publishing Corp, 1955.

[0070] 3. Gettens, R. J. Amer. Antiquity 27, 557-564, 1962.

[0071] 4. Gettens, R. J., Stout, G. L. Painting Materials: A ShortEncyclopedia D. van Nostrand, New York, N.Y., 1946.

[0072] 5. Gyenis, J., Gyenis. J. Bulk Solids Mixing Imperial CollegePress, 1999.

[0073] 6. Iinoya, K., Masuda, H., Watanabe, K. Powder and Bulk SolidsHandling Processes Marcel Dekker, Jul. 1, 1988.

[0074] 7. Josè-Yacamán, M., Rendón L., Arenas, J., Carmen, J., Puche, M.C. S. “Maya Blue Organic/inorganic Complex Paint: An AncientNanostructured Material” Science Vol. 273, 223-225, 1996.

[0075] 8. Lamboume, R., Strivens, T. A. Paint and Surface Coatings:Theory and Practice, 2^(nd) ed. William Andrew, 1999.

[0076] 9. Littman, E. R. Amer. Antiquity 45, 87-101, 1980.

[0077] 10. Littman, E. R., Amer. Antiquity 47, 404-408, 1982.

[0078] 11. Herman, M. F., Encyclopedia of Polymer Science andEngineering, 2 ^(nd) ed. John Wiley & Sons, 1990.

[0079] 12. Mindess, S., and Young, J. F. Concrete Englewood Cliffs,N.J.: Prentice-Hall, Inc., 1981.

[0080] 13. Olphen, Van H. Science 154, 645-646, 1966a.

[0081] 14. Olphen, Van H. American Antiquity 645-646, 1966b.

[0082] 15. U.S. Pat. No. 3,950,180

[0083] 16. U.S. Pat. No. 5,061,290

[0084] 17. U.S. Pat. No. 4,246,036

[0085] 18. U.S. Pat. No. 4,640,862

[0086] 19. U.S. Pat. No. 4,868,018

[0087] 20. U.S. Pat. No. 4,874,433

[0088] 21. U.S. Pat. No. 5,574,081

[0089] 22. U.S. Pat. No. 5,972,049

[0090] 23. U.S. Pat. No. 5,993,920

[0091] 24. U.S. Pat. No. 6,339,084

[0092] 25. U.S. Pat. No. 6,402,826

[0093] 26. Ramachandran, V. S., and Feldman, R. F. Cement Science, InConcrete Admixtures Handbook: Properties, science, and technology ParkRidge, N.J.: Noyes Publications, 1-54, 1984.

[0094] 27. Scientific American Discovering Archaeology, p.4, August2000.

[0095] 28. Shepard, A. O. Amer. Antiquity 27, 565-566, 1962.

[0096] 29. Taylor, The Chemistry of Cements, 2 volumes, London: AcademicPress W. F. W., ed. 1964.

[0097] 30. Torres, L. Maya Blue: How the Mayas Could Have Made thePigment, Materials Research Society Symposium Materials ResearchSociety, 1988.

[0098] 31. U.S. Department of Transportation, Federal HighwayAdministration, Portland Cement Concrete Materials Manual Report no.FHWA-Ed-89-006, Washington: FHWA, August, 1990.

[0099] 32. Weinekotter, R., Gericke, H. Mixing Of Solids (PowderTechnology Series, Number 12), Kluwer Academic Publishers, 2000.

[0100] 33. Zollinger, H. Color Chemistry, 2 ^(nd) ed., John Wiley & Son,1991.

What is claimed:
 1. A coating composition comprising: a) a molecularderivative of indigo; and b) a fibrous or layered clay; wherein saidcoating composition is used for coloring surfaces.
 2. The coatingcomposition of claim 1, wherein the color/hue of said composition isdetermined by the concentration of said dye and pH of said composition.3. The coating composition of claim 1, wherein the particle size of saidcoating composition is between 0.01 μm and 20 μm.
 4. The coatingcomposition of claim 3, wherein the particle size of said coatingcomposition is between 0.1 μm and 2 μm.
 5. The coating composition ofclaim 1, wherein said fibrous clay is a palygorskite clay, a sepioliteclay, or a mixture of a palygorskite and a sepiolite clay.
 6. Thecoating composition of claim 1, wherein said layered clay is akaolinite, bentonite, nontronite, or mordenite clay.
 7. The coatingcomposition of claim 1, wherein said molecular derivative of indigo isdibromoindigo or thioindigo.
 8. The coating composition of claim 1,wherein the coating composition is a powder or a liquid.
 9. The coatingcomposition of claim 1, wherein said coating composition is resistant todecomposition by light.
 10. The coating composition of claim 1, whereinsaid coating composition is resistant to decomposition by acids,alkalis, and solvents.
 11. A composition comprising:

R₁-R₈ are individually H, CH₃, CH₂CH₃, F, Cl, Br, I, CN, OH, SH, OCH₃ orOCH₂CH₃; R₉-R₁₁ are individually SiO₃, SiOH or H₂O; Y is N, O, S, or Se;X is O or S; M^((n+)) is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Pt, Pdor Zn; and n is 1, 2, 3 or
 4. 12. A formulation comprising: a) amolecular derivative of indigo; b) a palygorskite clay, a sepioliteclay, or a mixture of a palygorskite and a sepiolite clay; c) a polymer;and d) an organic binding agent.
 13. A formulation comprising: a) amolecular derivative of indigo; b) a palygorskite clay, a sepioliteclay, or a mixture of a palygorskite and a sepiolite clay; and c) a gumarabic; a linseed oil; a copal; a polycarbonate; an egg tempura; or aturpentine.
 14. A shapeable molding material comprising: a) a molecularderivative of indigo; b) a palygorskite clay, a sepiolite clay, or amixture of a palygorskite and a sepiolite clay; and c) a cement, aplastics or a polymer.
 15. A shapeable tile material comprising: a) amolecular derivative of indigo; b) a palygorskite clay, a sepioliteclay, or a mixture of a palygorskite and a sepiolite clay; and c) acement, a plastic or a polymer.
 16. A method of producing a coatingcomposition comprising: a) obtaining a molecular derivative of indigo;b) combining said molecular derivative of indigo with a fibrous orlayered clay to form a coating composition; c) heating said coatingcomposition; and d) adjusting the pH of the dye or pigment composition.17. The method of claim 16, further comprising treatment of said coatingcomposition with acid to remove impurities from the clay.
 18. The methodof claim 16, further comprising applying said coating composition to asurface.
 19. The method of claim 16, further comprising blending saidcoating composition with a polymer or organic binder.
 20. The method ofclaim 16, further comprising homogenizing said dye composition byblending, grinding, milling or stirring.
 21. The method of claim 16,wherein said heating comprises heating at a temperature of between 100°C. and 300° C.
 22. The method of claim 21, wherein the temperature isbetween 115° C. and 150° C.
 23. The method of claim 16, wherein saidheating lasts a maximum of four days.
 24. The method of claim 16,wherein said coating composition contains water.
 25. The method of claim16, wherein said coating composition has a pH between 3 and 7.5.
 26. Themethod of claim 16, wherein said coating composition contains a dye inthe range of 0.01% to 20% by weight.
 27. The method of claim 16, whereinsaid coating composition contains a molecular derivative of indigo inthe range of 0.1% to 7% by weight.
 28. The method of claim 16, whereinsaid coating composition contains a molecular derivative of indigo atabout 6% by weight at neutral or acidic pH.
 29. The method of claim 16,wherein said fibrous clay is a palygorskite clay, a sepiolite clay, or amixture of a palygorskite and a sepiolite clay.
 30. The method of claim16, wherein said layered clay is a kaolinite, bentonite, nontronite, ormordenite clay.
 31. The method of claim 16, wherein the particle size ofsaid coating composition is between 0.01 μm and 20 μm.
 32. The method ofclaim 31, wherein the particle size of said coating composition isbetween 0.1 μm and 2 μm.
 33. The method of claim 16, wherein saidmolecular derivative of indigo is thioindigo or dibromoindigo.
 34. Themethod of claim 16, further comprising adding a binding agent to saidcoating composition.